Air launched radio station



82 60 E grwmbow PERCIVAL D. LQWELL WILLIAM HAKKARINEN QJJJLLL 5 sheets-sheet l FIG. I

P D LOWELL ET AL AIR LAUNCHED RADIO STATION FIG. 2

June 5, 1951 Filed June 20, 1945 June 1951 P. D. LOWELL ETAL 2,555,352

AIR LAUNCHED RADIO STATION I Filed .June 20, 1945 5 Sheets-Sheet 2 FIG.3

June 5, 1951 P. D. LOWELL ETAL AIR LAUNCHED RADIO STATION 5 Sheets-Sheet55 Filed June 20, 1945 R. FAME RESPONSIVE RESISTANCE FIG. IO

TO GROUND FIG.|O

FIG. II

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96 PERCIVAL D. LOWELL WILLIAM HAKKARINEN 5 Sheets-Sheet 4 gmwww PERCIVAL-D. LOWELL WILLIAM HAKKARlNEN P D LOWELL ETAL AIR LAUNCHED RADIO STATIONJune 5, 1951 Filed June go, 1945 June 1951 P. D. LOWELL ETAL 2,555,352 4AIR LAUNCHED RADIO STATION Filed June 20, 1945 5 Sheets-Sheet 5 TORELAXATION OSCILLATOR GRID FIG. II

To enouuo FIG. I:

TO FILAMENTS OF TRANS- MITTER TUBES FIG."

g wcwvtow PERCIVAL 0. LOWELL WILLIAM HAKKARINEN m QLL L p Patented June5, 1951 STATES AIR LAUNCHED RADIO STATION Percival D. Lowell, ChevyChase, and William Hakkarinen, Hyattsville, Md.

8 Claims.

Our invention relates to a radio station which may be dropped from anaircraft onto remote or hostile territory and there unattended will setitself into operation for transmission of signals, for example weatherdata such as pressure, temperature and humidity.

In accordance with one aspect of our invention, the station upon itsrelease from a bombrack, or equivalent support, floats by parachuteuntil contact with the earth initiates a series of events, including forexample, release of the parachute, and elevation of an antenna,culminating in transmission, preferably periodically, of weather data orother intelligence.

Further in accordance with our invention, the release of the parachute,the elevation of the antenna and erection of the station, when erectinglegs are employed, are efiected by explosive charges under control of atiming device, preferably the same device which controls the periods oftransmission and silence of the radio transmitting equipment.Precautionary measures are taken to insure the explosive means aredisabled until after the station is clear of the aircraft.

Further in accordance with our invention, to insure accuracy of thetransmitted data despite possible deformation of relatively movablecontacting parts due to landing impact, those parts are vibrated toensure their proper relative posi tion in response to change inpressure, temperature or humidity, even though the deformation maygreatly vary the contact pressure.

In accordance with other aspects of our invention, it is provided thatchange of electrical characteristics of circuit components aftercalibration shall not affect accuracy of the transmitted data and thatresponse of the temperature element shall not be substantially afi'ectedby incident radiation.

Our invention further resides, in features of construction, combinationand arrangement hereinafter described or disclosed.

A later form of our invention having additional features not hereinshown is disclosed in copending application Serial No. 613,151, filedAugust 28, 1945, by Robert P. Bennett.

Referring to the drawings:

Figure 1 is a general vertical sectional view showing the location ofthe various major components in one embodiment of our invention. Theview shows the appearance of the device while being lowered by parachuteand before the legs or antenna have assumed their erected positions.

amended April 30, 1928; 370 0. G. 757) Figure 2 shows the weatherstation after erection of the legs and antenna.

Figure 3 is an enlarged sectional view taken on section 3-3 of Figure 1showing the para chute release pin and the tension spring used to ejectthe parachute cable.

Figure 4 is a sectional view taken on section 4-4 of Figure 1 showingthe parachute release pin and the explosive charge used to release theparachute.

Figure 5 is an enlarged sectional view taken on section E5 of Figure 1showing the means used to release the legs.

Figure 6 is a vertical sectional view of the telescoping antenna and theassociated reservoir.

Figure 7 is a detailed sectional view of one of the joints of theantenna shown in Figure 6.

Figure 8 shows in partial section the housing used for thetemperature-sensitive resistance element.

Figure 9 shows the pressure-sensitive device and the associated variableresistor.

Figure 10 shows the circuit used to provide sequential operation of theerecting and transmitting functions.

Figure 11 is a simplified schematic diagram of the relaxation oscillatorand crystal oscillator.

Referring now to Figure 1 of the drawings we have shown a generalsectional view of one embodiment of the device. It will be seen that thehousing is shaped in the manner'of a bomb. This structure is indicatedgenerally by the numeral 25! and consists of a nose portion 22, alongitudinal supporting member 2A, a transverse shelf or spider Z6, andlongitudinal s11e1f-sup-- porting straps 26. A yoke Elli connecting thespider 2b and the nose portion 22 is provided to enable attachment tothe bomb rack of an aircraft. Two additional transverse shelves 32 and34 are used for the mounting of the Various components to be described.The compo nents are mounted so as to cause the center of gravity to beas close to the bottom as possible to increase the tendency of thedevice to remain upright. To make the device self-erecting without theuse of legs, the center of gravity may be lowered by the addition ofadditional weight 36 placed as low as possible and, in addition, thediameter of the nose may be considerably increased.

Provision is made at the end opposite the center of gravity for theattachment of a parachute (not shown) having shroud lines 33. The shroudlines are connected to a rigid rod 4 extending down into the center ofthe structure for attachment. The rod 40 extends sufficiently beyond thetop of the device so that the shroud lines 38 clear any componentsextending above the upper shelf 32. A lead line 42 is connected from ashroud to the dowel pin 44 of an arming switch 46, the functions ofwhich will be described below. During transportation the parachute ispacked in the space indicated generally by the numeral 48.

To erect the device, legs 50 are provided which are hinged to the spider26 by hinges 52; springs 5 are provided to bias the legs downwardlytoward the nose 22. The leg releasing mechanism indicated generally bythe numeral 56 controls release wires 58.

The pressure-responsive device I38, the temperature-responsive device 62and the humidity-responsive device 64 initiate the signals to betransmitted. These weather responsive devices are switched into theradio circuit by clock 66. The radio and electrical portion of thedevice is illustrated in block form in Figure l and consists of therelaxation oscillator 63, the transmitter IE, and the power supplyconsisting of dry batteries, I2. If desired the power supply may bemounted within the nose portion. The antenna for the radio transmitterconsists of a telescoping vertical antenna "I4 which is elevated bygases generated in the explosive reservoir "5%. Switch 18 consists ofconcentric annular contacts 80 designed to be shorted by the shortingstrips 82. This switch controls parachute release device 85.

Figure 2 shows the weather station in the erected position with the legs50 drawn downwardly by the action of springs E i and with the antenna Ii extended. The protection afiorded the weather responsive units by thelegs has been removed by erection and the elements are fully responsiveto ambient conditions.

Figure 3 shows in detail the device used for quickly releasing theparachute. A spring 86 is connected between the parachute rod 40 causingrapid ejection of the rod ii? upon removal of the pin 88. This springserves both to eject the rod without delay and to apply constant lateralpressure on pin 83 to prevent accidental displacement of the pin. Itwill be obvious to one skilled in the art that instead of using therigid rod extension it of the parachute line, much the same effect maybe achieved by using a line flexible all n the way to the point ofattachment to the release mechanism and by simultaneously increasing theupward extent of tube 24 suificiently to clear all obstructionsprojecting from the upper shelf 32. In lieu of extending tube 24 a leadthrough device or eyelet spaced from. shelf 32 could be used for thispurpose.

The specific explosive release device used is shown in Figure 4. Theexplosive is housed in chamber 90 and is fired by fusible link 92 towhich power is supplied by means of the electrical lead fl l. A similardevice is shown in Figure 5 for releasing the legs 50 held in positionby wires 58. The explosive contained in the chamber 96 is fired by thefusible element 98 supplied by electrical lead I03.

Figure 6 shows the telescoping antenna 14 and the reservoir I6. Anexplosive device I02 is used to provide gas pressure in the reservoir.This pressure feeds into the lower chamber I84 within the antenna barrel15 at a reduced rate due to the relatively restricted path presented bythe connecting tube I66. The antenna consists of a number of telescopingsections designated as I08, II 0, and H2 fittin within the barrel I5.

Gaskets H3 are provided to prevent the passage of gas between therespective walls of the tubes or sections. Split annular friction ringsH l are mounted in the annular retaining caps I I6 at the top of eachsection. An enlarged portion H8 is provided at the base of each sectionto engage the split rings I'M as later described. Apertures I26 areprovided to lead the expanding gas from each section to the sectionimmediately above.

The function of the split rings H4 is shown to better advantage inFigure 7. Full extension of any antenna section relative to an adjacentsection causes engagement of the enlarged portion H8 and the split rin II i. This frictional engagement has two useful effects. The first is toabsorb the kinetic energy or the moving antenna section, the second isto provide a frictional engagement which prevents the telescoping of thetwo sections with respect to one another except by the application ofintentional effort. In operation pressure created within the reservoir16 is applied to the lower chamber II'M of the antenna barrel 15. Due tothe obstruction of the rapid flow of gases caused by interconnectingtube I06, the antenna barrel I5 and its sections I08 and Ht may beconstructed of relatively light gauge material. Pressure in the chamberI04 is immediately effective toraise the first section I08 of theantenna. Admission of gas pressure to the chamber I22 immediately aboveis hindered by the relatively constricted orifice I28. Gas pressureappears in the second chamber I22 only after the high initial gaspressure has been effective to overcome any static friction existingbetween the first movable section I68 and the antenna barrel 55.

Figure 8 shows a detailed view in partial cross section of the housingfor the temperature-responsive element. The housing consists of spacedoverlapping cup members I24 surmounted by a cover I26. The outer surfaceof each cup member is provided with a light-reflecting surface. Theinner surface may be darkened to prevent the reflection of lightreceived from the outer surface of the cup immediately below to thetemperature-sensitive element 134. Each cupshaped member is providedwith a radially extending flange I28. Longitudinal pins I30 en gage theflanges and spacing is provided by the Washer-like spacers I323. Theresistance element I34 sensitive to changes in temperature isresiliently suspended within the housing by any suitable means of lowheat conductivity.

Figure 9 is a detailed view of the pressure-responsive device 613. Itcomprises a frame I36 to which a bellows I38 is attached by means of abracket I60. The free end of this bellows terminates in'an axiallymovable rod I412 pivoted to a resistance-controlling lever M6. Thecollar I 46 is provided on the movable rod I42 to interfere with bracketI48 and thus prevent excessive expansion of the bellows when the deviceis carried at high altitudes. Lever I44 is effective to vary the wirewound resistance element I50. A buzzer I52 is mounted to cause vibrationjust prior to the insertion of resistor I50 into the relaxationoscillator circuit. Such vibration overcomes both the friction in thebearings, which may be increased by deformation of the members uponimpact of the weather station upon the ground. The tensile spring I54takes up the slack in the mechanical system. The hygrometer orhumidity-sensitive device 54 also includes a buzzer to overcome theeffect of friction. The hygrometer may be of the well known hair typeand may move a resistance-controlling arm in the same manner as thepressure responsive device.

Figure shows the switching system used to provide sequential operationof the explosive de vices and sequential transmission of weather data.An electric clock I 54 provided with two sets of contacts performs theswitching operation. The hour hand I55 makes contact with contacts I 51once every three hours in the embodiment described while the minute handI58 makes contact once every minute after the first contact of theseries is engaged. Current is supplied to the winding I59 of the clockfrom battery I60, relay current is supplied by battery I62, and filamentand fuse current is supplied by battery I 64. All three batteries aredisconnected from their respective circuits by the action of the triplepole single throw arming switch 45, which is energized as the weatherstation is dropped from the aircraft.

Assuming that the hour hand I56 has made contact, negative potentialwill appear on the minute hand I58. As the minute hand touches the firstcontact IE6, relay I68 is energized, picking up contacts I It. Closingof these contacts supplies potential from battery IM to the fusible link92 of the parachute releasing device 84. The making of the first contactis a safety precaution; the fuse 92 will normally have been operated byclosing of the nose switch 18 upon contact with the ground. The secondcontact I12 is effective to energize the leg release relay II l. Thisresults in the closing of contacts I I6 and the firing of the fusibleelement 98 in the leg releasing device. Contact of the minute hand I58with the third contact I'IB causes the picking up of the relay I80, theclosing of contacts I82 and the firing of the antenna-erecting explosivedevice I 02. Contacts controlling other erecting functions could beincluded if necessary at this point.

The subsequent making of the contact I8 3 causes relay I86 to beenergized, which in turn closes contacts I88, putting the referenceresistance ISil into the grid circuit of the relaxation oscillator aswill be described. Contact I92 causes energization of relay I94, theclosing of contacts I 93 and the insertion of the pressureresponsiveresistor I98 into the oscillator grid circuit. In like manner contacts2G0, 203, and 2I6 through the medium of relays 202, 2H], and ZIB causethe respective insertion of the temperature-responsive resistor 206, thehumidityresponsive resistor 2 I i, and the identification resistor 222,into these circuits. The final making of contact 224 causes reinsertionof the reference resistor I90.

It will be noted that the firing of the leg re- ].easing fuse 98 isaccompanied by operation of the buzzer or vibrator I52 associated withthe pressure-responsive device 61]. In like manner, a buzzer 226 placedin parallel with the antenna erecting fuse I02 is effective to vibratethe humidity responsive device 64. It will also be noted that thebuzzers I52 and 226 operate for an extended period, approximately 45seconds, prior to the insertion of the associated resistance into therelaxation oscillator grid circuit. The vibration counteracts frictionand enables the weatherresponsive device to assume a true equilibriumposition.

The filaments of the transmitter tubes are turned on by relay 228 whichis in series with the resistance-switching relays I86, I94, 202, M0, and2 I 8. Thus, filament power is applied only during periods of actualtransmission, as will be seen below, thereby saving the battery Hit. Byputting the hands of the clock I56 and I58 in series as shown, thesequence described above will only take place once every three hours.

Figure 11 shows the relaxation oscillator circuit designated generallyas 230, the crystal oscillator circuit 232 and the radio frequency '(R.F.) amplifier 234. The relaxation oscillator comprises a vacuum tube 236of any well known type having a high value of trans conductance and atransformer 238, consisting of windings 2 3D and. 242. The time constantof the oscillator is determined by the capacitor 242 and the resisterwhich may be inserted into the circuit. Such resistor, indicatedgenerally by numeral 246, may be any one of the resistors I82, I98, 2&5,22M, or 222, discussed in connection with Figure 10. The use of smalladditional, capacitors 241i and 258 in a relaxation oscillator circuitis well known. A relay 252 is provided in. the plate circuit of therelaxation oscillator tube. The contacts 252 of this relay short out thegrid bias ap plied through resistor 255 associated with the crystaloscillator tube 256 to start oscillation of the crystal oscillatorcircuit. The interrupted oscillations are amplified and broadcast by theradio frequency amplifier 234.

The relaxation oscillator operates as follows: Assuming a suddenapplication of plate voltage, increasing plate current will result in apositive potential being applied to the grid of vacuum tube 235. Thispositive potential will result in the fiow of grid current which chargescapacitor 244. When the plate current becomes constant at a saturatedvalue, no positive voltage is induced at the grid terminal of thesecondary 245-2 of the transformer. The plate current will there forestart to decrease, such decrease inducing a negative potential at thegrid of the tube cutting off the plate current. The plate curreht iskept in the cut-off condition by the negative charge which has collectedduring the previous half cycle on the capacitor 242. This charge isdissipated through resistor 24% and, after the time interval requiredfor such dissipation, the grid will lose its negative potential and. thecycle will be repeated. The capacitor 244 the time constant circuit islarge, on the order of 8 microfarads, while the resistor 24%: is on theorder of 10,000 ohms. This results in a desirable slow pulse rate on theorder of to 3 pulses per second.

Before use the relaxation oscillator is calibrated with theweather-responsive elements so that each condition of pressure,temperature, and humidity corresponds to a certain pulse rate. Thealtered characteristics of other components in the circuit, caused forexample by aging or damage, may cause a pulse rate somewhat slower orfaster than the calibrated value for a given value of grid resistor.This error may be elin1i nated by the use of the reference resistorI983. The pulse rate resulting from the insertion of the referenceresistor Hill in the grid circuit is noted at the time of initialcalibration. Later in actual use the reference resistor Ififi isswitched into the grid circuit by the clock 55 i prior to the resistorsassociated with the weathe --sensitive devices. If it is noted that thepuls rate for the reference resistor is, say, 5 percent too the pulserate noted for each of the other store will be corrected by beingreduced proportionately before the pulse rate is interpreted as aweather condition.

The intended use of the device is as follows: The weather station withits legs 50, held in the position shown in Figure 1 and with theparachute packed in space 48 provided, is loaded on the bomb rack of anaircraft. A static line is rigged from the aircraft to the parachute topull the parachute free immediately after the device is released. A leadline 42 is attached to one of the shrouds 38 of the parachute and to thedowel pin M which holds the arming switch 56 in an open position thuspreventing the batteries from energizing any of the circuits. The clockIM may be present to energize the associated leg or antenna-erectingcontacts after a dormancy period of up to approximately three hoursafter the arming switch ii has been operated.

When a suitable location for the station has determined, the station isdropped. The static line causes the parachute to open lowering thestation at a rate of approximately 8 feet per second. At the same timeopening of the parachute causes arming switch 46 to apply power to startthe clock i 3 and to connect batteries M59, M22, and Mid into thecircuit. Upon impact with the ground, the nose switch l5 will close,firing the parachute releasing device 84 and preventing the station frombeing pulled along the ground. The device will lie inert for the ore-setdormancy period until the first contact 566 is made by the clock I54. Along dormancy period may be 01 use where it is intended that the devicelie unerected until darkness has fallen in order to escape enemydetection. Contact I56 is effective to release the parachute is noseswitch 78 has failed to do so.

Contact of the minute hand with the second terminal. N2 of the clockwill cause operation of the leg release device 56. Assuming that thedevice has landed on its side, the release of the 5% will. due to theurging of springs Ed. cause the device to become upright as shown inFigure 2. This be readily accomplished by springs 5d of this size if thedevice has a low center of gravity.

As the minute hand of the clock touches the third contact 2'58, theantenna erecting explosive device iii-'2 is fired causing erection ofthe antenna as discussed above.

lhe contact of the minute hand with contacts E92, 28d, 2&3, 255, and 22%results in the consecutive insertion of the reference resistor I99, thepressure-responsive resistor I98, the temperature-responsive resistor268, the humidity-responsive resistor 2M, and the identificationresistor While it will be obvious to one skilled in the art that thespacing of the clock contacts and the contact Width may be adjusted overwide limits, the following program has been found to be satisfactory:

Signal Timc (approximate) While the identification signal which notifiesthe operator to which station he is listening has a separate resistor inthe embodiment described. the identification function could also beperoil 3 formed by using a distinctly difierent pulse rate for thereference signal of each weather station used.

At the receiving station the transmitted pulses are counted over ameasured time interval and the pulses per unit time readily computed.Calibration charts enable the pulse rates to be inter-- preted asweather conditions. Assuming that dry batteries are used, reasonablebattery power is suflicient to cause the station to transmit the aboveprogram of signals every 3 hours for a period in excess of 15 days.

When the station is to be used only as a beacon, the radio transmitterand its control mechanisms may be simplified merely to transmit a signalwhich may be used to guide for example other craft equipped withradio-direction-fiinding apparatus.

While we have shown and described particular embodiments of ourinvention, it will occur to those skilled in the art that variouschanges and modifications can be made without departing from ourinvention, and we, therefore, aim in the appended claims to cover allsuch changes and modifications that follow in the true spirit and scopeof our invention.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

What we claim is:

1. An automatic radio station adapted to be lowered by parachutecomprising, an elongated housing having its center of gravity near thebottom end, a parachute suspension line having its point of exit at thetop end of said housing remote from said center of gravity, an explosivepara chute release device to release said suspension line, a noseportion on said housing at said bottom end, a set of electrical contactsmounted on said nose portion to operate said release device upon contactwith the earth, a quick acting fusible element in said explosive releasedevice operated by said electrical contacts whereby positive release isobtained with only momentary contact of said electrical contacts.

2. An automatic radio station adapted to be lowered by parachutecomprising an elongated housing having its center of gravity near itsbottom end, a plurality of legs hingedly attached to said housing atspaced points about said housing at a level above said center ofgravity, said hinge attachment enabling each of said legs to swing in aplane which includes the axis of said housing, biasing means to urgesaid legs toward said bottom end of said housing, retaining means tohold said legs along the side of said housing against the action of saidbiasing means, and releasing means operable after contact with the earthto erect said housing into a leg-supported position.

3. An automatic radio station adapted to be lowered by parachutecomprising an elongated housing including a frame, a parachutesuspension line, a parachute suspension line lead through device mountedat the end of said housing at a point spaced surficiently far from theend of said housing so as to minimize the possibility of fouling of saidsuspension line with components projecting from the end of said housing,a parachute suspension line engaging member engaging said suspensionline and mounted within said housing at a point of great mechanicalstrength of said frame whereby the likelihood of damage to said housingcaused by the jerk of said parachute suspension line upon opening ofsaid parachute is reduced.

4. The subject matter as claimed in claim 3 including a spring havingone end engaging said parachute suspension line within said housing andthe other end engaging said lead through device whereby said suspensionline is quickly and forcibly ejected from said lead through device uponrelease of said line from said line-engaging member.

5. An automatic radio station adapted to be lowered by parachutecomprising an elongated housing including a frame, a parachutesuspension line, a parachute suspension rod fastened at the end of saidsuspension line to support said housing, said rod projecting outwardlyfrom said housing to a point sufficiently far from said housing as tominimize possible fouling of said suspension line with componentsprojecting from the end of said housing, said parachute suspension rodprojecting into said housing to a point of great mechanical strength ofsaid frame, a parachute release device engaging said rod and mounted atsaid point of great mechanical strength, and a spring having one endengaging said parachute suspension rod within said housing and the otherend engaging said housing at the point of entry of said rod, wherebysaid suspension rod is quickly and forcibly ejected from said housingupon release of said rod by said parachute release device.

6. An automatic radio station adapted to be lowered by parachutecomprising a housing, a nose portion on one end of said housing, aparachute supporting line entering said housing at a point remote fromsaid nose portion, an explosive parachute release device engaging saidparachute supporting line, a set of electrical contacts mounted on saidnose portion to energize said explosive release device upon impact withthe earth, an arming switch mounted on said housing having electricalcontacts in series with said nose electrical contacts, an arming switchoperator engaging said parachute supporting line effective to cause saidarming switch to close upon opening of said parachute, whereby operationof said explosive release device is not possible until after saidstation is parachute-supported.

7. An automatic radio station adapted to be lowered by parachutecomprising a housing, a parachute supporting line engaging said housing,an explosive release device to free said parachute supporting line fromsaid housing, an explosive erecting device to erect said station foruse, an arming switch having electrical contacts in series with saidexplosive release device and said explosive erecting device, an armingswitch operator engaging said parachute supporting line and effective tocause said arming switch to close upon the opening of said parachute,whereby operation of any explosive devices is not possible until aftersaid station is parachute-supported.

8. An automatic self-erecting radio station adapted to be dropped byparachute from aircraft comprising, an elongated housing having itscenter of gravity near its bottom end, a plurality of legs hingedlyattached to said housing at spaced points about said housing at a levelabove said center of gravity, spring biasing means urging said legs tobe swung outwardly from said housing toward said bottom end of saidhousing for the purpose of self-erection and support, retaining meansefiective until said station is dropped to hold said legs adjacent thesides of said housing against the action of said biasing means, saidlegs being of such length and so positioned as to project beyond the topend of said housing forming a receptacle for the temporary storage of aself-contained parachute.

PERCIVAL D. LOWELL. WILLIAM HAKKARINEN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,709,264 Holt Apr. 16, 19292,118,603 Hailey May 24, 1938 2,169,904 Schweller Aug. 15, 19392,228,060 Lescher et a1. Jan. 7, 1941 2,232,693 Dow Feb. 25, 9412,300,847 Russel Nov. 3, 1942 2,311,491 Turner Feb. 16, 1943 2,327,163Barrett Aug. 17, 1943 2,352,891 Graves July 4, 1944 2,373,413 PlummerApr. 10, 1945 2,381,009 Siderman N Aug. 7, 1945 2,399,221 Freas Apr. 30,1946 2,402,143 Arenstein June 18, 1946 2,452,990 Bush Nov. 2, 19482,492,501 Robins Dec. 27, 1949

